Contention: Ethernet
The critical parameter for a CSMA/CD is the round-trip time for a signal to get from one node to another and back
After a maximum round-trip time without a collision, a sender knows it has acquired the medium
For the ethernet this time is ~ 50 ?s = 64 bytes at the 10 Mbits/sec transmission time
- Maximum diameter of 2 km = 10 ?s
- at 5 ?s/km for signal propagation in cable
- 10 ?s for the time a receiver needs to read the ‘preamble’ of the packet and either synchronize with the clock or detect a collision, and
- 5 ?s to pass through a maximum of two repeaters, which is 25 ?s, times 2 for the round trip.